2 stroke rattle noise

[770]

There is a noise in the engine that runs with the rpm, when I rev, it ticks faster. I can also hear this noise when I ride. I have checked for slack in crank on both sides, changed piston, the conrodl and the whole clutch side. Also checked for engine mounts. It still runs normally and starts as usual. Can the main bearings be bad anyway? I'm starting to run out of ideas here ..

sound:

https://www.youtube.com/watch?v=P4L8OUs6HK0

[Vincent]

Piston slap?
Little ends?

Mains tend to make more of a rumbling noise. Yours deffo sounds like top-end from where I'm sitting.
____________________
Space Is Deep

[770]

[Vincent]

Maybe you should take the top end off again and make sure the circlip hasn't come out or a ring snapped.
____________________
Space Is Deep

[770]

[Vincent]

Are you sure it isn't something vibrating on the outside of the engine?
____________________
Space Is Deep

[770]

[-]

A couple of options. Firstly, if you changed the small end bearing, what about the gudgeon pin? I normally change piston, rings, small end, pin and circlips at the same time.

Also, has it been rebored? On some engines with high squish, the standard size head gasket needs honing out a bit to match the size of the over bored piston, or the top end of the piston can catch it.

Main bearings are normally more of a knocking, rumbling noise than that.

When you changed the piston was there any damage? A small piece of ring may have ended up in the crank and has now found it's way up to the combustion chamber through a transfer port and is now merrily bouncing about.
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[770]

[-]

So it's on standard bore then?
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[770]

[-]

[770]

an O-ring head, so obviously no change there, but squish on a peaky engine like that will be pretty tight. A slightly thinner base gasket could lower the barrel enough so the piston touches the outside of the squish band. [/quote]

Maybe you could poke a bit of solder through the plug hole so it touches the edge of the barrel and turn over by hand to measure the squish in 2 or 3 places around the top of the bore?[/quot

It's a Husky 125cc, I think they only sell one kind of base gasket.
The noise suddently came after a ride, not after a rebuild. 4000km ago the crankshaft, bearings, piston were changed.

[Vincent]

If you're sure it's not the top end, and it's definitely coming from the bottom, I suppose it has to be the main bearings as there's not much else down there. I suppose with a smaller engine, main bearing wear may sound a bit less "rummbly".
Where is the water pump?
____________________
Space Is Deep

[bikenut]

seen video but no audio here........our computer......

1.does it make the noise if the flywheel cover is off??

2.is anything under the flywheel touching anything else??

3.how about on the primary drive side, anything in there involved with the crank touching anything else, apart from gear teeth to gear teeth or balance system?

4.sure its not an exhaust leak?

5. reeds?

6.did you check for "bump clearance"? yes I know its a petrol engine but still??
____________________
nuts about bikes

[Vincent]

Try using something as a stethoscope, a bona-fide stethscope works best but as most people don't have one, try a large screwdriver with a solid handle......... sticking the end of the handle on your ear. it'll help to locate the area the rattle's comng from.
____________________
Space Is Deep

[770]

[770]

[bypass2]

What about your clutch basket loose pull the clutch in then rev it a few times see if it still happens. engine chain sprocket loose.

[bikenut]

not able to hear the audio......

do you reckon the noise is at crankshaft speed??

does it make the noise if the engine is off but bike is pushed along in gear? with plug out?? and ign killed..
____________________
nuts about bikes

[-]

Having listened to the second video, that is more of a rumble now. I'd be guessing at big end or main bearings now. Big end should be fairly obvious if you pop the barrel off and check for movement in the con rod.

I'm not sure no side to side movement in the crank would mean the main bearings are good.

Sometimes, disconnecting the primary drive, piston and generator rotor, you can then turn the crank and by hand and feel a tight spot or rough running on the bearings without having to split the crankcase. If the con rod feels OK, then main bearings at a guess.

Time for a strip down though. Top end first.
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[bladerunner]

just for interest..did you actually measure the piston and bore to work out the clearance?
____________________
Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[770]

The bike felt like it was surging, when I was going to clutch out from first it sounded like I needed to choke it. When turning it off I heard this squeaky noise, and everytime I kickstart it this squeak comes and the engine stops after a few seconds..

I have already checked clutch, piston, conrod, flywheel. Basically everything you can check without splitting.

VIDEO
https://youtu.be/VcQao433GjQ

[-]